Concrete is one of the most popular flooring materials due to its durability and ease-of-maintenance. But before concrete floors are ready for use, they undergo processes and treatments to perform and look good.
Polishing a concrete floor is like polishing a wooden floor. The idea is to achieve a smooth and glossy finish. But unlike polishing wood, polishing concrete involves specialized equipment such as a power grinder, grinding discs, and a power buffer. Also, the process is a lot more involving and time-consuming as concrete is harder compared to wood.
The following is a comprehensive step-by-step process to guide if you decide to do DIY concrete polishing.
Step 1: Determine the hardness of the concrete using a MOHS test kit
Determining the hardness of the concrete helps you pick the right grinding discs. You can buy a MOHS (measure of hardness scale) test kit online or at your local hardware store.
The kit has several picks, labeled from #1 to #9. Start with the #9 pick and draw a line on the concrete surface applying the same pressure you would if you were using a pencil. Look or feel for a scratch. Work your way down the pick numbers in descending order until you find a pick that does not scratch the surface.
If the #6 pick leaves a scratch, but the #5 does not, it means your concrete floor has a hardness rating of 5.5. Test the hardness on at least three different areas of the floor to get an average hardness rating.
A 7.5 or higher hardness rating means the concrete is hard, while 5.5 or lower means the concrete is soft.
Step 2: Rent a concrete grinder with the right grinding discs
Grinding helps achieve the right exposure before polishing the concrete. It also removes the existing concrete coating.
Since a concrete grinder is expensive, it does not make sense to buy one for a one-time project. The best option is renting from a hardware store or specialized tool rental retailers.
Make sure you test the grinder before renting it. Also, ask for instructions on how to use it and the precautions you should take.
Additionally, make sure you get metal-bonded diamond grinding discs. Other discs are not strong enough to effectively grind concrete.
Grinding discs range from 40- to 3000-grit—the lower the grit number, the coarser the disc. So, pick a set of grinding discs that will suit the hardness of your concrete based on the MOHS test you conducted.
Step 3: Clean the concrete floor with soap and water
Thoroughly clean the concrete surface with soap and water using a bristle brush. Remove any stubborn stains using a stain remover with hydrogen peroxide or trisodium phosphate (TSP). Wear protective gear when using a stain remover.
Rinse the surface with clean water and allow it to dry.
Step 4: Check for surface damages and potential hazards
Cleaning the surface allows you a better look at the concrete surface. Inspect the surface for damages such as cracks and hazards such as protruding reinforcement bars.
For cracks not wider than a quarter-inch, you will need a concrete crack filler and caulk gun to apply. If the cracks are wide, you will need a concrete patching product, which you will apply and smooth with a trowel.
Allow the filler or patch to cure before you start grinding. The cure time will be indicated on the product’s package.
Protruding metals on the surface have to be chipped and cut out. We recommend letting a professional handle a floor with protruding reinforcement bars.
Step 5: Start grinding using a coarse grinding disc
The grinding process produces a lot of dust. Additionally, the grinder is loud and can cause serious injury if used the wrong way. Therefore, before you start grinding, put on protective gear, i.e., a dust mask, safety goggles, earplugs, thick protective gloves, a helmet, and non-slip work shoes. You should also read the user’s manual for further instructions on how to use the grinder.
Start grinding in half-circle movements using a coarse disc. The 40- or 80- grit will help remove the existing concrete coating and other surface imperfections that soap and water could not remove.
Start grinding from one corner and gradually move forward while ensuring that you are grinding evenly.
Step 6: Repeat the grinding process using each disc in your set
Repeat the grinding process with the next grinding process and work your way to the highest value in your set. For instance, if you started with the 40-grit, progress to the 80-grit, then 150-grit, and so on. When you change to a new disc, begin at the corner adjacent to the one you started with the last disc.
A new disc buffs the scratches left by the last disc, ultimately achieving a fine surface ready for polishing.
Step 7: Apply a concrete densifier
A densifier hardens and seals the concrete making it not only impervious but also less likely to form dust. Follow the manufacturer’s instructions to apply the densifier. That said, most densifiers are applied using a sprayer. You will also have to allow the densifier to dry before proceeding to the next step.
The best time to apply the densifier depends on the hardness of your concrete floor. If the concrete is hard, apply the densifier after grinding using the 400-grit, after the 200-grit for medium, and 80-grit for soft concrete.
Step 8: Grind one final round using the 3000-grit disc
This step is optional. However, the 3000-grit disc is so fine that it starts polishing the concrete. It helps the polishing product achieve a glossier finish.
Step 9: Vacuum the concrete surface
Before you start the actual concrete polishing, vacuum the surface to remove all dust and debris from the grinding. Cleaning before moving to the next grinding disc is unnecessary and too much work. It is only convenient if you have a grinder with a built-in vacuum cleaner. Either way, after the final round of grinding, you have to clean the surface using a wet-dry vacuum cleaner.
Step 10: Buff the concrete surface
Attach a burnishing pad to the grinder and use half-circle motions to buff the entire concrete surface. However, some renters do not have burnishing pads or have grinders that cannot use burnishing pads. The best option in such cases is a brush-style low-speed power buffer.
Buffing further smoothens the surface in readiness for the sealer.
Step 11: Apply a concrete sealer
A sealer protects the concrete while also helping create a glossier polished concrete surface. Read the manufacturer’s instructions to determine whether the sealer requires a roller or a sprayer. Evenly apply the sealer in a thin coat and wait for about 2 to 4 hours (depending on the manufacturer’s instructions) before applying the second coat.
Most sealers will dry within 2 to 4 hours, depending on the temperatures. We recommend applying the sealer when the temperatures are above 50 degrees.
Step 12: Buff the surface again for a glossier finish
After the sealer dries, buff the surface one more time to achieve a glossier finish. Buff thoroughly, making sure you cover the entire surface.
Do you have the skills and time needed for DIY concrete floor polishing? Concrete polishing is not a simple DIY project. For the best results, hire a professional concrete flooring contractor, such as Brand North. We provide professional concrete polishing services in Hempstead and surrounding areas.
There are also lots of options for metallic epoxy floors. Here is an example from one of our manufacturers and it will detail the reasons you probably SHOULD NOT do this project yourself: